python-cachelock
================
[](https://pypi.python.org/pypi/cachelock)
[](https://travis-ci.org/douglasfarinelli/python-cachelock)
[](https://coveralls.io/github/douglasfarinelli/python-cachelock?branch=master)
[](https://pypi.python.org/pypi/cachelock)
The `cachelock` serves to ensure that your code block or function is executed one at a time using the cache as acquirer.
How to install:
===============
pip install cachelock
or
pipenv install cachelock
How to use
==========
You can use of two forms:
- Use the `Lock` class to your blocks;
- Or use the decorator `once` to block your functions or tasks;
With cachelock.Lock
===================
Arguments:
with cachelock.Lock(
key=...
cache=...,
) ...
You should use the Lock class as with context:
with cachelock.Lock(key='foo'):
...your code ...
If it is already locked, the LockError will be raised.
With cachelock.once
===================
Arguments:
@cachelock.once(
key=...
cache=...,
raises_if_lock=False
)
...
With the decorator, you can guarantee the unique execution of some function. It also allows you to configure your key according to the arguments of the function.
@celery.task
@cachelock.once(key='foo-{arg_a}-{arg_b}')
def func(arg_a, arg_b):
pass
That way, if it is locked, the function quits silently. You can also ask `once` to raise `LockError`:
@celery.task
@cachelock.once(
key='foo-{arg_a}-{arg_b}',
raise_if_lock=True
)
def func(arg_a, arg_b):
pass
Integrate with Django
=====================
The cachelock checks whether django is installed, and if so, it uses django's own cache as aquirer. And if you wish, you can modify the default cache with `DEFAULT_CACHELOCK_ALIAS` configuration through django settings. The value must be an alias of some existing cache, by default it uses `default`
*Remembering that by `default`, `cachelock` uses its own internal cache in memory if there is no integration with `django`.*
Customizing your own cache
==========================
To work it is necessary that the implementation of the cache has the `get`, `delete` and `set` methods. Ex.:
class DummyCache:
def set(self, key, value):
pass
def get(self, key, default=None):
pass
def delete(self, key):
pass
cache = DummyCache()
use:
@cachelock.once(key=..., cache=cache)
or
with cachelock.Lock(key..., cache=cache) ...
